The estimate of impedance and kick factors of the recently installed at KEK Photon Factory (PF) four In-Vacuum Undulators (IVU) is currently a very important issue, because they could be considerable contributors to the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for the accurate estimate of its effects on the beam quality and beam instabilities and also for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.

Updated Model of the Resistive Wall Impedance for the Main Ring of J-PARC

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B. Yee-Rendón, Y.H. Chin, H. Kuboki, T. Toyama
KEK, Ibaraki, Japan

M. Schenk
CERN, Geneva, Switzerland

The resistive wall impedance is one of the major contributors of the impedance in the Main Ring of J-PARC. The present model assumes round chambers of stainless steel with perfect magnet boundary conditions for its surroundings. This work presents the model of the resistive wall impedances taking into account the different chamber geometries of Main Ring, the materials and more realistic surroundings. The models were benchmarked with measurements of the coherent tune shift of the Main Ring of J-PARC. The simulation of beam instabilities is a helpful tool to evaluate potential threats against the machine protection of the high intensity beams.

Accelerator physics needs advanced modeling and simulation techniques, in particular for beam stability studies. A deeper understanding of the effects of magnetic fields nonlinearities will greatly help in the improvement of future colliders design and performance. This paper presents a study of quadrupole tracking using realistic field maps and measured or simulated longitudinal harmonics. The main goal is to describe the effect of the longitudinal dependence of high order non-homogeneity of the field in the case of the HL-LHC inner triplet.

The Planned upgrade of the Advanced Photon Source to a multi-bend achromat (MBA) will increase the x-ray brightness by two to three orders of magnitude. Storing such an intense beam stably inside the narrow gap vacuum chambers requires sophisticated and appropriately designed rf-components that helps to minimize rf heating and collective instabilities associated with the impedance of these small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. In this paper, we briefly introduce the novel Goubau line (G-line) test fixture for the impedance measurement, at first, and then present our measurements data along with simulations with simulations for various vacuum components designed for the APS Upgrade.

Funding:This project is now supported by the COST Action CA15139/EuroNuNet and EU/H2020 innovation programme ESSnuSB under grant agreement No 777419.The ESSnuSB project, recently granted by the EU H2020 framework programme for a 4-year design study, proposes to use the proton linac (2 GeV, 5 MW) of the European Spallation Source (ESS) currently in construction in Lund (Sweden) to deliver a neutrino super beam. One of the work packages of this design study is dedicated to the primary proton beam-line completing the linac. It will mainly consist of an accumulator ring to compress the 2.86 ms long beam pulse to 1.32 μs and of a switchyard to distribute the protons onto a 4-target station. Dipoles, steerers, quadrupoles, collimators and several diagnostics will compose the switchyard to ensure the protons to hit the target with desired characteristics. This paper presents the objectives of this work package and the design status of this switchyard system.

The CYRCé cyclotron is used at IPHC (Institut Pluridisciplinaire Hubert Curien) for the production of radio-isotopes for diagnostics, medical treatments and fundamental research in radiobiology. The TR24 cyclotron manufactured and commercialized by ACSI delivers a 16-25 MeV proton beam with intensity from few nA up to 500 microA. The TR24 is a separated-sector isochronous cyclotron with normal-conducting magnet and stripper foil. It is a challenge to fit the high intensity proton beam used for target irradiation to radiobiology and analytical applications due to requirements on beam quality and energy resolution. Field distribution in the region of the extraction performed with OPERA 3D as well as beam dynamics related with stripping are analysed. 3D calculation model and hypothesis about geometry and beam are described. Our goal is to evaluate the extraction efficiency and the beam characteristics in the focusing plane outside the cyclotron which will serve as inputs for the design of future beam lines and enable beam matching conditions. Therefore, different issues are discussed: energy dispersion, transverse dynamics and orbit separation.

For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 105 MeV for physics experiments with an internal target. We will discuss matching conditions with space charge together with the estimated microbunching gain for the arc. The implication for the ERL operation will be outlined, using 3D envelope and tracking simulations.Supported by the DFG through GRK 2128

Funding:French ANR, Investissements d'Avenir, EQUIPEX. Contract number ANR-11-EQPX-0012.The new ISOL facility SPIRAL2 is currently being built at GANIL, Caen France. The commissioning of the accelerator is in progress since 2015. SPIRAL2 will produce a large number of new radioactive ion beams (RIB) at high intensities. In 2023, the DESIR facility will receive beams from the upgraded SPIRAL1 facility of GANIL (stable beam and target fragmentation), from the S3 Low Energy Branch (fusion-evaporation and deep-inelastic reactions). In order to deliver the RIB to the experimental set-ups installed in the DESIR hall, 140 meters of beam line are studied since 2014. The transfert lines are today fully design and building will start in 2018. Electrostatic devices (quadrupoles, steerers and deflectors) have been intensively study using various tools. This paper will focus on the detail results of a benchmark using OPERA3D and Comsol Multiphysics apply to the DESIR quadrupole conception.

Funding:Program for the National Science Foundation of China (Grant No. 11105019) and the National Science Device Exploitation Foundation of China (Grant No. 2011YQ130018).A high power THz free electron laser (FEL) facility is under construction at China Academy of Engineering Physics (CTFEL) since October, 2011. The radiation frequency of the FEL facility will be tuned in range of 1~3 THz and the average output power is about 10 W. The system mainly consists of a GaAs photoemission DC gun, superconductor accelerator, the hybrid wiggler, optical cavity. The first lasing is obtained on Aug. 29, 2017. The optical resonator of CTFEL is optimized to ensure wavelength tunable in a wide range and high power operation. The FEL power strongly depends on the performance of the optical resonator including output efficiency, gain and round-trip loss. The optical resonator consists of metal-coated reflect mirror, the center-hole output mirror, waveguide. The influence of waveguide and Rayleigh length on the quality of optical cavity is evaluated by the 3D-OSIFEL code. The waveguide size, mirror curvature radius, output hole radius is optimized to different frequencies between 1 THz to 3 THz.

The High Energy Photon Source (HEPS) is a new designed photon source at beam energy of 6 GeV, with natural beam emittance less than 100pm. Due to the small transverse beam size, beam ion instability is one of the potential issues for HEPS. The growth time of the instability is estimated analytically for different operation scenarios. The results show considerably good agreement with the wake strong simulations.

In the High Energy Photon Source (HEPS), strip-line kickers are adopted for beam injection and extraction. Beam coupling impedance contribution from the strip-line kicker is calculated. Detailed studies on the heat load dissipation have been performed. The peak electric field on the blade and the induced voltage on the feedthroughs due to the beam passage are also calculated.

Coherent synchrotron frequency shift is observed during machine studies in BEPCII (Beijing Electron Positron Collider Upgrade). The results show that the synchrotron frequency varies parabolically with the increase of the beam current. This phenomenon is supposed to be induced by the interaction of the beam with the fundamental mode of the accelerating cavity. In order to explain this phenomenon, a simple physical model is developed from the couple bunch instability theory. The analytical estimations based on the physical model show good agreement with the measurements.

Funding:Work supported by Natural Science Foundation of China，No.11505253The study of higher order modes excited in the China-ADS Linac has been presented in this paper. The effects of the cryogenic losses and the influence on beam of the higher order modes have been investigated.

Funding:This project has been supported by TUBITAK with project number 114F106 and 117F143.DEMIRCI software aims to aid RFQ design efforts by making the process easy, fast and accurate. In this report, DEMIRCI 8-term potential results are compared with the results provided by other commercially available simulation software. Computed electric fields are compared to the re- sults from simulations of a recently produced 352 MHz RFQ. Recent developments like the inclusion of space charge ef- fects in DEMIRCI beam dynamics are also discussed. More- over, further terms are added to 8-term potential to simulate possible vane production errors. The FEM solver was also improved to mesh the cells with errors.

The installation of the IFMIF-EVEDA RFQ, MEBT, LEBT, source and beam dump was completed in September 2017. The beam dynamics of the first beams for the IFMIF-EVEDA RFQ commissioning is presented. Moreover, a proposal for the CW RFQ steady state commissioning is shown, with a focus on the beam dynamics challenges of the beam transport after the RFQ.

The different components of the DAΦNE accelerator complex: LINAC, Damping Ring and two colliding rings are connected by a composite system of Transfer Lines which, thanks to adaptive configurations, are able to transport electron and positron beams at 510~MeV. Recently, thanks to the introduction of new diagnostics tools, the optics model of the DAΦNE Transfer Lines has been improved and succesfully used to make the collider operations more efficient. The measurements done by using the new tools and their impact on the optics model optimization process are presented and discussed.

Within the framework of the SPES (Selective Production of Exotic Species) project at National Institute of Nuclear Physics (INFN laboratory, Legnaro, Italy) the High Resolution Mass Spectrometer (HRMS) will be build. HRMS needs to provide full separation of the ions with mass resolution 1/20000 for the following breeding and acceleration on ALPI Linac. In this article the main design choice of the HRMS and of the transport channel will be reported.

Beam Dynamic Simulation for the Beam Line from Charge Breeder to ALPI for SPES Project

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M. Comunian, L. Bellan, A. Pisent
INFN/LNL, Legnaro (PD), Italy

A.V. Ziiatdinova
ITEP, Moscow, Russia

A.V. Ziiatdinova
MEPhI, Moscow, Russia

The SPES project (Selective Production of Exotic Species) is under development at INFN-LNL. This facility is intended for production of neutron-rich Radioactive Ion Beams (RIBs) by ISOL method. The +1 charged beam will be transformed to n+ charge by Charge Breeder (Electron Cyclotron resonance ion source) and reaccelerated by the ALPI (Acceleratore Lineare Per Ioni) superconducting Linac . This paper includes results of beam dynamic simulation at the beam line from Charge Breeder to ALPI.

The PADME experiment* proposes a search for the dark photon (A') in the e+e− -> gamma A' process in a positron-on-target experiment, exploiting the positron beam of the DAΦNE linac at the Frascati National Laboratory. The linac could provide a number of positrons as high as 109/pulse in a 200 ns pulse but the number of positrons for PADME is limited below 105/pulse in order to keep the pile-up probability in the calorimeter low enough. The PADME experiment is indeed limited by the low duty factor (10e-5=200ns/20ms). An alternative proposal to use the DAΦNE positron ring as a linac pulse stretcher, by injecting each pulse into the ring and extracting it by a slow resonant extraction using the m/3 resonance, is described in this paper. This allows to distribute the positrons of a linac pulse in a much longer pulse (0.2 - 0.5 ms) increasing the duty factor up to ~ 2%. The required modifications of the DAΦNE positron transfer line and main ring are presented. A dedicate lattice for the ring has been designed and tracking of the positrons in the ring has been performed to optimize extraction parameters and give a preliminary estimate of the extracted beam characteristics.* M. Raggi et al., EPJ Web Conf. 96 (2015) 01025

The Simulator of Particle Orbit Dynamics (S-POD) is a linear Paul trap at Hiroshima University, Japan, used to study beam physics. S-POD has so far been used to study resonances in high intensity beams, predominantly using a simple alternating gradient lattice configuration. Recently a similar apparatus, the Intense Beam Experiment (IBEX), has been constructed at the Rutherford Appleton Lab in the UK. To use either of these experiments to study beam dynamics in more complex lattice configurations in the future further diagnostic techniques must be developed for Paul traps. Here we describe a new method to measure the beta function and emittance at a given time in a Paul trap.

Funding:Work supported by Science and Technology Research council grant 'The John Adams Institute for Accelerator Science' ST/P00203X/1 and Impact Acceleration Account.Beam Delivery Simulation (BDSIM) is a program to seamlessly simulate the passage of particles in an accelerator, the surrounding environment and detectors. It uses a suite of high energy physics software including Geant4, CLHEP and ROOT to create a 3D model from an optical description of an accelerator and simulate the interaction of particles with matter as well as the production of secondaries. BDSIM is used to simulate energy deposition and charged particle backgrounds in a variety of accelerators worldwide. The latest developments are presented including low-energy tracking extension, more detailed geometry, support for ion beams and improved magnetic fields. A new analysis suite that allows scalable event by event analysis is described for advanced analysis such as the trace back of energy deposition to primary particle impacts.

In 2015 the joint project JINR (Dubna, Russia) - ASIPP (Hefei, China) on design and construction of supercon-ducting proton cyclotron SC202 was started. Two cyclo-trons are planned to be manufactured in China, according to the Collaboration Agreement between JINR and ASIPP. The first cyclotron will be used for proton therapy in Hefei and the second one will replace the Phasotron in the research and treatment program on proton therapy in Dubna. New schema of extraction system and results of beam acceleration and extraction simulations for Dubna cyclotron are presented.

Funding:Funded by BMBF (grant: 05K16VKA) & Helmholtz (contract: VH-NG-320). Supported by the Helmholtz International Research School for Teratronics & Karlsruhe School of Elementary and Astroparticle Physics.At the KIT storage ring KARA (KArlsruhe Research Accelerator), the momentum compaction factor can be reduced leading to natural bunch lengths in the ps range. Due to the high degree of longitudinal compression the micro-bunching instability arises. During this longitudinal instability the bunches emit bursts of intense coherent synchrotron radiation in the THz frequency range caused by the complex longitudinal dynamics. The temporal pattern of the emitted bursts depends on given machine parameters, like momentum compaction factor, acceleration voltage, and damping time. In this paper the influence of the damping time is studied by utilizing the CLIC damping wiggler prototype installed in KARA as well as by simulations using the Vlasov-Fokker-Planck solver Inovesa.

The operation of synchrotron light sources with short electron bunches increases the emitted CSR power in the THz frequency range. However, the spatial compression leads to complex longitudinal dynamics, causing the formation of micro-structures in the longitudinal bunch profiles. The fast temporal variation and small scale of these micro-structures put challenging demands on their observation. At the KIT storage ring KARA (KArlsruhe Research Accelerator), diagnostics have been developed allowing direct observation of the dynamics by an electro-optical setup, and indirect observation by measuring the fluctuation of the emitted CSR. In this contribution, we present studies of the micro-structure dynamics on simulated data, obtained using the numerical Vlasov-Fokker-Planck solver Inovesa, and first applications on measured data. To deal with generated data sets in the order of terabytes in size, we apply the machine learning technique k-means to identify the dominant micro-structures in the longitudinal bunch profiles. Following this approach, new insights on the correlation of the CSR power fluctuation to the underlying longitudinal dynamics can be gained.

In the UVSOR electron storage ring, which is dedicated for a VUV synchrotron radiation light source, a longitudinal coupled bunch instability (LCBI) is observed in multi-bunch operation. To suppress the LCBI, we routinely operate a third harmonic cavity (HCV) in a passive mode. By properly tuning HCV, the instability is almost completely suppressed. Because of the lower beam energy (750 MeV) and brilliant beam emittance (17.5 nm-rad), the Touschek effect becomes severe in the UVSOR. To guarantee enough beam lifetime, we also apply HCV for lengthening the bunch. The suppression of the instability and increasing the beam lifetime are crucial benefits by HCV for the UVSOR. However, not only the origin of the LCBI but also the Landau damping effect by HCV has not been understood systematically yet. We have noticed that one of the HOMs at HCV itself could cause the LCBI and observed the behavior of the instability, which strongly depends on the beam current. From the experiment we have discussed the cause of the instability with the HOM theory. We have also tried to observe synchrotron tune spread and discussed a competition between the Landau damping and the instability growth.Present affiliation of the first auther : Karlsruhe Institute of Technology

Funding:Funded by the German Federal Ministry of Education and Research (Grant No. 05K16VKA) & Initiative and Networking Fund of the Helmholtz Association (contract number: VH-NG-320).Solving the Vlasov-Fokker-Planck equation is a well-tested approach to simulate dynamics of electron bunches self-interacting with their own wake-field. Typical implementations model the dynamics of a charge density in a damped harmonic oscillator, with a small perturbation due to collective effects. This description imposes some limits to the applicability: Because after a certain simulation time coherent synchrotron motion will be damped down, effectively only the incoherent motion is described. Furthermore - even though computed - the tune spread is typically masked by the use of a charge density instead of individual particles. As a consequence, some effects are not reproduced. In this contribution, we present methods that allow to consider single-particle motion, coherent synchrotron oscillation, non-linearities of the accelerating voltage, higher orders of the momentum compaction factor, as well as modulations of the accelerating voltage. We also provide exemplary studies - based on the KIT storage ring KARA (KArlsruhe Research Accelerator) - to show the potential of the methods.

J.-B. Lagrange
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

In scaling FFAG* accelerators, ideally, betatron tunes are fixed for each closed orbit concerned with the certain beam energy. Therefore, they should not vary during the acceleration. However, it is not the case since practical implementations of the magnetic field can not provide perfect scaling conditions. There are two types of radial scaling FFAG ring at Kyoto University Research Reactor Institute: one has no return yokes so called 'yoke free type' adopted by MAIN RING which has a large tune variations causing non negligible beam losses; the other has return yokes and filed clamps adopted by BOOSTER RING which has smaller tune variations compared with MAIN RING. We report the tune measurements and calculations based on 3-d magnetic field calculations about these two types of ring and discuss the scaling conditions in FFAG accelerators.FFAG* : FFAG stands for fixed filed alternating gradient. It describes one the focusing scheme in the circular accelerator.

Funding:This work is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics.The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Several new numerical tools have been implemented in the code IMPACT-Z to allow for high-fidelity modeling of the IOTA ring during Phase II operation with intense proton beams. A primary goal is to ensure symplectic treatment of both single-particle and collective dynamics. We describe these tools and demonstrate their application to modeling nonlinear integrable dynamics with space charge in IOTA.

Accurate Modeling of Fringe Field Effects on Nonlinear Integrable Optics in IOTA

3294

C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA

F.H. O'Shea
RadiaBeam, Santa Monica, California, USA

Funding:This work is supported by the U.S. Department of Energy, Office of High Energy Physics.The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Uncontrolled nonlinear effects resulting from magnetic fringe fields can affect the integrability of particle motion, and long-term numerical tracking requires an accurate representation of these effects. Surface fitting algorithms provide a robust and reliable method for extracting this information from 3-dimensional magnetic field data provided on a grid. These algorithms are applied to investigate the unique nonlinear magnetic insert of the IOTA ring, and consequences of the fringe fields to the long-term dynamics of the beam are discussed.

The ALS-U is a major upgrade of the LBNL ALS to a diffraction limited light source. The current plan is to replace all the vacuum and magnet components while retaining the existing 500 MHz main and third-harmonic, passively operated, rf cavities, but replacement of the existing rf cavities is also being considered. A new feature, is represented by beam-loading transients associated with a beam consisting of 11 bunch trains separated by 10 ns gaps as needed to enable on-axis swap-out injection. In this paper we study these transients and the associated bunch-to-bunch phase, length, and profile variations.

The space-charge driven envelope instability presents a great danger in high intensity accelerator design. In this paper, we report on the study of bunched beam envelope instability in a periodic focusing channel using three-dimensional envelope model for a 3D uniform Waterbag distribution and a 3D Gaussian distribution. Our results show that the envelope instability stopband becomes broader with the increase of longitudinal focusing and are not sensitive to the type of distribution. Self-consistent macroparticle simulations using both distributions show similar structure in emittance growth but also extra instability stopbands. The emittance growth from the Waterbag distribution has larger stopband than that from the Gaussian distribution.

The nonlinear space-charge effects in high intensity accelerator can degrade beam quality and cause particle losses. Self-consistent macroparticle tracking simulations have been widely used to study these space-charge effects. However, it is computationally challenging for long-term tracking simulation of these effects. In this paper, we study a fully symplectic self-consistent particle-in-cell model and numerical methods to mitigate numerical emittance growth. We also discuss about a fast alternative frozen space-charge model that has a potential to improve computational speed significantly.

The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.

In this paper we describe a parallel, large-scale simulation capability using a Lienard-Wiechert Particle-Mesh (LWPM) method. The approach is a natural extension of the convolution-based technique to solve the Poisson equation in space-charge codes. It provides a unified method to compute both Coulomb-like self-fields and radiative phenomena like coherent synchrotron radiation (CSR). The approach brings together several mathematical and computational capabilities including the use of integrated Green function (IGF) methods and adaptive quadrature methods. We will describe the theoretical model and our progress to date.

Funding:This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.In this paper we summarize the current beam operation capability of FXR linear induc-tion accelerator (LIA) at LLNL. Experi-mental measurements for electron beam pa-rameters at different beam operations are pre-sented.

The ion-hose instability has long been considered a danger for long-pulse, high-current electron linear induction accelerators (LIAs)*. This instability is enabled by beam-electron ionization of residual background gas in the accelerator. The space-charge of the high-energy beam ejects low-energy electrons from the ionized channel, leaving a positively-charged ion channel that attracts the electron beam. The beam can oscillate in the potential well around the channel position. Likewise, the electron beam attracts the ions, which can oscillate about the beam position. Because of the vast differences in particle mass, the oscillations are out of phase, and the amplitudes grow unstably. The number of instability e-foldings is proportional to the channel ion density*, which in turn is proportional to the background pressure and pulse length. This scaling of the instability growth was demonstrated on the long-pulse DARHT-II linear induction accelerator (LIA) at Los Alamos**. The ion-hose instability is also problematic for high-current multi-pulse LIAs, because ion recombination times are so very long at typical background pressures. Moreover, because of low ion channel ion densities, and massive ions, channel expansion is too slow to reduce the instability growth by very much. In particular, the ion channel is expected to persist and its density to increase during the 3-microsecond duration of a four-pulse burst from the 2-kA, 20-MeV Scorpius LIA now being developed. Recent simulations with an experimentally validated code that was used to predict DARHT-II growth rates have shown that the magnetic focusing field designed for Scorpius will be strong enough to inhibit ion-hose instability if the background pressure is kept below a value that is readily attainable with the present designs of induction cells and other accelerator components. Details and results of these calculations are the subject of this presentation.*H. L. Buchanan, Phys. Fluids, vol. 30, pp. 221 - 231, 1987 **C. A. Ekdahl, et al., IEEE Trans. Plasma Sci., vol. 34, pp. 460-466, 2006

Funding:*Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.The Proton Radiography (pRad) experimental facility beam transport line is over 80 meters in length starting from the end of the LANSCE linear accelerator. The 800-MeV beam is transported through a beam line containing many bending and focusing elements before it reaches the pRad beam optics system where the beam spot size requirement is nominally 2 mm (RMS). Here we discuss the efforts to reconcile the beam transport inconsistencies (sizes) seen between comparisons of the beam sizes obtained using the LANL version of the beam envelope code TRANSPORT with those measured along the beam line. The transverse input beam parameters for the code were extracted from a fit to several wire-scanner measurements located in the downstream portion of the LINAC. The longitudinal input beam parameters were extrapolated from lower-energy information. Recently, new measurements were made of the beam line element locations and compared with legacy drawings. Beam envelope measurements made at various locations throughout the beam line using wire scanners and gated imaging systems were compared to the calculated results. The predicted beam envelopes and measured data agree within expected errors.*Los Alamos National Laboratory (LA-UR-17-30876)

Funding:Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DESC0000661.We are planning to use two types of the accelerator simulation codes for FRIB (Facility for Rare Isotope Beams). One is the linear envelope tracking code "FLAME" for fast simulations. FLAME can calculate the FRIB-linac beam envelope within an order of ms. This is useful in systematic surveys, wide range optimizations and so forth. This code, written in C++, was designed with Python interface from the beginning. On the other hand, "Advanced-IMPACT" is the particle tracking code dedicated for precise and realistic calculations, which can simulate the particle losses, nonlinear and space-charge effects. This code is refactored from the Fortran code IMPACT-Z developed in LBNL. Both codes provide the compiled modules for Python to support flexible inputs and direct outputs management in memory. In other words, they can be directly connected to the modern scientific tools through the Python interface without delay in the data transport. In addition, these modules can accomplish the interactive simulation processes without losing computational efficiency. We report the knowledges applicable for other accelerator simulation codes among those obtained through these developments and designs.

MuSim is a new and innovative graphical framework that permits the user to construct, explore, optimize, analyze, and evaluate nuclear, accelerator, and other particle-based systems efficiently and effectively. It is designed for both students and experienced scientists to use in dealing with the many modeling tools and their different description languages and data formats. Graphical interfaces are used throughout, making it easy to construct the system graphically, display the system with particle tracks, analyze results, and use on-screen controls to vary parameters and observe their effects in (near) real time. Such exploration is essential to give users insight into how systems behave, and is valuable to both new users and experienced system designers. The use of URL-based component libraries will encourage collabor-ation among geographically diverse teams. This project will facilitate access to advanced modeling and simulation tools for inexperienced users and provide workflow management for them and advanced users.

Computer simulation of electrons from explosive emission acceleration and X-ray quantum generation in pulse coaxial diode system with interior anode, which is used in accelerating tube of compact X-ray generator* with Tesla transformer as high voltage source, was done. The results obtained allow us to choose accelerating tube diode system geometry for different running modes. Comparison of numerical results with experimental data of dose rate dependence on the distance from vacuum tube anode and energy at first circuit Tesla transformer was fulfilled.*Patent RF N71817, 03.10.2007

FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.

The Taiwan Photon Source (TPS) is a low-emittance 3-GeV light source at National Synchrotron Radiation Research Center. Five in-vacuum undulator beamlines were delivered to users on Sep. 22, 2016. Another 2 EPU beamlines will be open to user in near future. In the beginning, the local bump was used to do ID spectrum optimization since 2016. After this procedure, the ID spectrum are consistent between theoretical simulation and measurement. Recently, we found the local bump will cause tune shift and orbit distortion. In this paper, we will present the effect of local bump in TPS.

In order to provide short-pulse radiation for pump-probe experiments and coherent radiation for THz/IR measurements, we develop low alpha lattices to reduce the momentum compaction factor from nominal operation values 2.4*10-4 to 2.6*10-5 or lower. The corresponding bunch length at 2.8 MV RF voltage and zero current are from 10.78 ps to 3.55 ps or less. In the low alpha operations, the bunch lengthening as a function of bunch current, the orbit drift and noise enhancements as well as rf stability effect are observed. In this report we will present our studies on the lattice design, optics correction, beam parameters measurements and alpha measurements.

Collective beam instabilities could limit the accelerator performance if proper countermeasures are not in place. Active beam feedback systems are commonly used to suppress beam instabilities. The resistive wall impedance including phase-II insertion devices at TPS are calculated with analytical formulas. The growth rate of transverse coupled bunch instabilities due to wall impedance is estimated by theory. The RF properties of existing stripline kickers in TPS are analyzed with a 3-D electromagnetic simulation code GdfidL. Based on the above analysis, the requirements for a beam feedback system are calculated and the results are reported.

In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.

Fermilab is pursuing a proof-of-principle test of the Optical Stochastic Cooling (OSC) of 100 MeV electrons in the Integrable Optics Test Accelerator. In support of this we present simulations of horizontal damping with OSC. We find excellent agreement with theory on the amplitude dependent damping rates. Additionally particle tracking is used to confirm the necessity and effectiveness of sextupoles used to correct non-linear path lengthening in the OSC chicane.

Amplification of beam-induced radiation (e.g. synchrotron or undulator radiation) is a necessary component of optical stochastic cooling of hadrons or heavy ions. We discuss a proposal to measure and amplify synchrotron radiation from a bending magnet of the Advanced Photon Source. The measurements will be in the short-wavelength infrared region (SWIR) and amplification will be accomplished using a pumped Chromium:Zinc Selenide (Cr:ZnSe) crystal with maximum gain at λ≅ 2.2~μm.

In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides additional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facility are presented and compared with numerical simulations.

Funding:This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.Canonical angular momentum (CAM) dominated beams can be formed in photoinjectors by applying an axial magnetic field on the photocathode surface. Such a beam possess asymmetric eigenemittances and is characterized by the measure of its magnetization. CAM removal using a set skew-quadrupole magnets maps the beam eigenemittances to the conventional emittance along each transverse degree of freedom thereby yielding flat beam with asymmetric transverse emittance. In this paper we report on the experimental generation of CAM dominated beam and their subsequent transformation into flat beams at the Fermilab Accelerator Science and Technology (FAST) facility. Our results are compared with numerical simulations and possible applications of the produced beams are discussed.

Funding:This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.Flat beams can be produced via a linear manipulation of canonical angular momentum (CAM) dominated beams using a set of skew-quadrupole magnets. Recently such beams were produced at Fermilab Accelerator Science and Technology (FAST) facility. In this paper, we report the results of flat beam compression study in a magnetic chicane at an energy of E~32 MeV. Additionally, we investigate the effect of energy chirp in the round-to-flat beam transform. The experimental results are compared with numerical simulations.

Funding:Work supported by the Grant from Russian Foundation for Basic Research (No. 17-52-04107).The interaction of relativistic electrons with periodic structures results in radiation by a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by distance between crystallographic planes and direction of electron beam. If instead of crystal one considers a periodic structure of metallic wires with period of the order of mm, one can expect emission of THz radiation. In the present contribution we consider theoretical approaches for modeling of the distribution of electromagnetic field from electron bunches in lattice formed by metallic wires. The analytical description is possible for the case of wires with small radius, the range of validity is checked by numerical simulations. The intensity of radiation will be significantly increased if the electrons in the bunch could radiate coherently. Two possibilities will be discussed: the prebunching of the beam and the self-modulation of the beam due to interaction with radiated field.

Nano-structured cathodes can form transversely modulated beams which can be subsequently converted to temporally modulated beam via a transverse-to-longitudinal phase space-exchanging beamline. We demonstrate via numerical simulation the generation of transversely modulated beam at the nm scale and investigate the corresponding enhancement in a soft-X-ray SASE free-electron laser. Our study is supported by start-to-end simulation combining WARP, IMPACT-T and GENESIS(FEL process) and focuses on the optimization of the beamline to preserve initial modulation at the nanometer level. We also discuss the scaling of the concept to shorter-wavelengths.

Funding:ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the US DOE. This research was supported by the DOE Office of Science, Accelerator and Detector Research Program.We have proposed to inject a self-consistent "rotating" beam into the Spallation Neutron Source (SNS). Self-consistent beam distributions are defined to be ellipsoidal, or elliptical in 2D, distributions that have uniform density and that retain these properties under all linear transformations. We have made much progress since the original proposal. We have demonstrated computationally the feasibility of injecting a rotating beam under realistic physics assumptions. We have optimized the injection scheme with respect to beam loss and to minimum necessary hardware changes. We have also determined how existing SNS beam diagnostic equipment can be used to verify the self-consistency of the injected beam. This paper will report the details of this work as well as the status of plans to carry out the self-consistency experiments.

Funding:This work has been supported by Oak Ridge National Laboratory, man-aged by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.We derive a precise analytical nonlinear transverse map for single particle transport through a solenoid with hard edge fringe fields. The transfer map is two dimensional for transverse coordinates and momenta with fixed longitudinal momentum. Because it is an accurate analytic map, it is also symplectic. The transfer map is compared with ex-act numerical tracking.

The Open XAL accelerator physics software platform is being developed through an international collaboration among several facilities since 2010. The goal of the collaboration is to establish Open XAL as a multi-purpose software platform supporting a broad range of tool and application development in accelerator physics and high-level control (Open XAL also ships with a suite of general purpose accelerator applications). This paper discusses progress in beam dynamics simulation, new RF models, and updated application framework along with new generic accelerator physics applications. We present the current status of the project, a roadmap for continued development and an overview of the project status at each participating facility.

Particle bunches traveling in a ring can excite wakefields inside any radio-frequency element present. These electromagnetic modes can resonate long enough and interact with subsequent passing bunches. A coherent oscillation between bunches can quickly become an instability and needs to be addressed. The Jefferson Lab electron ion collider has a large 50 mrad crossing angle and thus relies on bunch crabbing to achieve high luminosity. Bunch crabbing is done with compact superconducting rf dipole cavities. We study coupled bunch oscillations driven by the higher order modes of multicell RFD crab cavities under study for JLEIC, we calculate the instability growth time assuming a symmetric beam spectrum, identify the HOMs driving the instability and discuss mitigation measures.

Funding:This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters.

By placing a cathode in a longitudinal magnetic field generated by a solenoid or permanent magnet, angular-momentum dominated electron beams can be produced. Such beams can be uncoupled using a skew-quadrupole channel to remove the angular momentum and yield flat beams with an ultralow emittance in one of the transverse dimensions. Flat beams have immediate relevance in our pursuit of ultrahigh brightness in two dimensions for dielectric laser accelerator (DLA) or slab beam applications. We are currently investigating the possibility of implementing flat beam generation at the UCLA Pegasus beamline. We utilize particle tracking simulations to optimize the transverse emittance ratio and normalized transverse emittance. Our simulations show emittance ratios of more than 100 and normalized emittances in the <5 nm range in the vertical dimension, matching analytic estimates. In addition to simulation results, experimental plans to implement and test the flat beam transform (FBT) are also discussed.

Several possibilities of manipulating the electron beam using sources of wakefield are being explored. Wakefield have been successfully used to remove or enhance the energy chirp residual from the magnetic compression to control the free electron laser bandwidth (dechirper), to linearize the compressed beam (linearizer), to generate more bunches to produce two color mode, and to perform experiments of wakefield acceleration. At the SwissFEL injector we plan to install 2 m long system to accommodate sources of wakefield with different periodicities, each of them associated with one of the discussed beam manipulation. In this paper we summarize the design and the characterization of the system and the planned activities.

High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to activation. For this reason, in the commissioning phase, a molecular hydrogen ion (H2+) beam is often used as a model for the deuteron beam without the radiation risk. However, composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Such interactions affect the beam dynamics results, and may lead to production of secondary particles, which in high-intensity beams may cause damage to the accelerator and reduce the quality of the beam. In order to understand these effects, we have modified the IMPACT-T particle tracking code to include particle interactions during the tracking simulation through a high-intensity continuous-wave (CW) radio-frequency quadrupole (RFQ). This code is also designed to be easily extensible to other interactions, such as collisions or break-up of heavier ions. Preliminary results and possibilities for future development will be discussed.

The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.

This paper studies if the vacuum chamber of an elec-tron storage ring can be made of dielectric non-meta materials such as ceramics or glass. The purpose of this study is to substantially reduce the broadband imped-ance of the vacuum chamber and consequently mitigate single bunch instabilities. This theoretical study examines how these materials can reduce the impedance and pro-poses how to resolve technical problems to occur.

For future applications of high-brightness electron beams, including the design of next generation FEL's, correct simulation of Coherent Synchrotron Radiation (CSR) is essential as it potentially degrades beam quality to unacceptable levels. However, the long interaction lengths compared to the bunch length, numerical cancellation, and difficult 3D retardation conditions make accurate simulation of CSR effects notoriously difficult. To ease the computational burden, CSR codes often make severe simplifications such as an ultra-relativistic bunch travelling on a prescribed reference trajectory. Here we report on a new CSR model implemented in the General Particle Tracer (GPT) code that avoids most of the usual assumptions: It directly evaluates the Liénard'Wiechert potentials based on the stored history of the beam. It makes no assumptions about reference trajectories, and also takes into account the transverse size of the beam. Example results demonstrating normalised emittance growth in the first bunch compressor of FERMI@Elettra are presented.

Funding:This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181.The particle tracking code Zgoubi*,** is used for a broad array of accelerator design studies, including FFAGs*** and EICs****,*****. In this paper, we describe recent work aimed at improving Zgoubi's speed and flexibility. In particular, we describe a new implementation of the Zgoubi tracking algorithm that requires significantly less memory and arithmetic. And we describe a new algorithm that performs symplectic tracking through field maps. In addition, we describe the current efforts to parallelize Zgoubi.*https://sourceforge.net/projects/zgoubi/ **F. Méot, FERMILAB-TM-2010, 1997 ***F. Lemuet et al., NIM-A, 547:638, 2005 ****F. Méot et al., eRHIC/45, 2015 *****F. Lin et al., IPAC17, WEPIK114, 2017

The Integrable Optics Test Accelerator (IOTA) is being commissioned at Fermi National Laboratory for study of the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The nonlinear element should provide suppression of instabilities through nonlinear decoherence. We examine the case of a bunch injected off-axis and the resulting damping of centroid oscillations from decoherence. A simple model of the damping is described and compared to simulation.

Funding:This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340.Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab.

We present a parallel fast Fourier transform based 3D space charge software library based on integrated Green functions. The library is open-source, and has been structured to easily be used by existing beam dynamics codes. We demonstrate this by incorporating it with the Bmad toolkit for charged particle simulation, and compare with analytical formulas and well-established space charge codes.

Correctly and rapidly simulating the steady-state interaction between particle beams and electromagnetic fields is crucial to the design and optimization of accelerator and radiofrequency (RF) source components. Iteratively solving for the self-consistent interaction between particles and fields can prove challenging and highly susceptible to numerical noise and mesh induced instabilities. We present herein two new approaches to solving the self-consistent trajectories of particles in the presence of external and self fields. The first method reformulates the integrated self field contribution as a path integral. The second method uses a hybrid Eulerian framework and produces an interpolated continuous current density, resulting in 1-2 orders of magnitude fewer particles required to obtain an accurate solution. We conclude with benchmarking results which show this method is as accurate as state of the art PIC solvers, while running 80-120X faster.

The spectrum of software packages for the physics of charged particles beams is extremely wide. From most popular and effective systems can be allocated such programs as COSY Infinity, MAD X, MARYLIE, TRANSPORT. Heterogeneous individual formats of input and output data, the lack of a common and user-friendly interface and the narrow specialization of these programs poses a number of challenges for the modern researchers. It significantly reduces the effectiveness and quality of corresponding computational experiments. In this article we present a universal tool for automation and acceleration of computing experiments. The authors consider a method for developing the concept and prototype of a corresponding software package that would combine the advantages of existing (non-commercial) systems. This software will be able to unify the input and output data format for certain programs, visualize the information in various ways, provide reference and training information for "beginners". The results obtained within the developed framework will be a significant contribution both to the development of numerical and symbolical methods for solving evolution nonlinear equations.

In the article, we propose an implementation of the matrix representation of Lie transform using TensorFlow as a computational engine. TensorFlow allows easy description of deep neural networks and provides automatic code execution on both single CPU/GPU and cluster architectures. In this research, we demonstrate the connection of the matrix Lie transform with polynomial neural networks. The architecture of the neural network is described and realized in code. In terms of beam dynamics, the proposed technique provides a tool for both simulation and analysis of experimental results using modern machine learning techniques. As a simulation technique one operates with a nonlinear map up to the necessary order of nonlinearity. On the other hand, one can utilize TensorFlow engine to run map optimization and system identification problems.

In this paper we propose a symbolic representation of the solutions of the equations of evolution of dynamical systems in the framework of matrix formalism and Lie algebra for a number of elements of the accelerator (in particular, dipole, quadrupole and octupole) up to the 4th order. The considered solutions are Lego-objects*, which are include into the general scheme of the representation beam dynamics. It allows modeling of schemes of various accelerators and thereby to increasing performance of parametrical optimization. Let us note that the symbolic approach to solving such problems is more preferable than the numerical one, which is widely used. This leads to a reduction in the time and resources spent on solving optimization problems, as well as the ability to create universal Lego objects. The paper considers the verification of the obtained formulas from the experimental data. The corresponding Lego objects are the main components of the special software for both symbolic and numerical dynamics analysis. This software is planned to be used for modeling within the framework of the NICA accelerator project.*S.N. Andrianov. Dynamic Modeling of Particle Beam Control Systems. Saint Petersburg State University, 2002.

The Large Hadron Collider (LHC) Injector Upgrade (LIU)Project at CERN calls for increasing beam intensity for the LHC accelerator chain. Some machine components will not survive the new beam characteristics and need to be rebuilt for the new challenging scenario. This is particularly true for beam intercepting devices (BIDs) such as dumps, collimators, and absorber/scrapers, which are directly exposed to beam impacts. In this context, this work summarizes conceptual design studies on the new Proton Synchrotron Booster (PSB) Absorber/Scraper (PSBAS), a device aimed at cleaning the beam halo at the very early stage of the PSB acceleration. This paper outlines the steps performed to fulfil the component design requirements. It discusses thermo-mechanical effects as a consequence of the beam-matter collisions, simulated with the FLUKA Monte Carlo code and ANSYS finite element software; and the impedance minimization study performed to prevent beam instabilities and to reduce RF-heating on the device.

The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In such a scenario, critical accelerator devices need to be redesigned and rebuilt. Impedance is among the design drivers, since its thermo-mechanical effects could lead to premature device failures. In this context, the current work reports the results of a multiphysics study to assess the electromagnetic and thermo-mechanical behaviour of the Target Dump Injection Segmented (TDIS). It first discusses the outcomes of the impedance analysis performed to characterise the resistive wall and the high order resonant modes (HOMs) trapped in the TDIS structures. Then, their RF-heating effects and the related temperature distribution are considered. Finally, mechanical stresses induced by thermal gradients are studied in order to give a final validation on the design quality.

The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed.

Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.

Funding:Supported by the National Natural Science Foundation of China (11375122, 11511140277)At the end of 2016, the first beam was extracted from the 3.0 MV Tandetron accelerator system at Sichuan University, China. The accelerator is imported from the HVEE as a multi-purpose research platform. For one of the main applications, the system will be connected to a micro-beamline to achieve submicron resolution, so the accelerator is designed with energy stability as high as 0.01%. The measured brightness for 3 MeV proton beam is 5.06 pA/um2mrad2MeV and the energy stability is reached the goal of design. The ion optic design of the microprobe beam line will be presented in this paper.

SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them.

A prototype of combined function magnet has been developed for a new facility of Siam Photon Source (SPS). The magnet is a combined dipole and quadrupole with the required dipole field and quadrupole gradient of 0.6 T and 30 T/m, respectively. The high field gradient is attained from an offset quadrupole design pioneered by the European Synchrotron Radiation Facility (ESRF). The prototype magnet is fabricated and tested in-house. Magnetic field quality is characterized by the field homogeneity in the central field region and multipole components of the magnetic field. Calculated results show that the gradient deviation and the normalized multipole error are less than 0.01 within the good field region of ±8 mm. Preliminary measurements show a good agreement with the calculation, although further measurements are required to verify the results and the multipole error of magnetic field.

Pragmatic Method of Deducing a Wake Function for a General 3D Structure

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G. Skripka
CERN, Geneva, Switzerland

R. Nagaokapresenter
SOLEIL, Gif-sur-Yvette, France

A key quantity in simulating collective beam instabilities is the wake potential of a bunch of particles whose charge distribution is continuously evolving in time. However, obtaining such wake potential is only possible if a wake excited by a single particle in the surrounding environment is known. A practical self-consistent approach was developed to obtain an effective wake function from a numerical wake potential computed for a finite length bunch. The wake potential is processed to a numerical impedance which is decomposed into a set of well-known analytical wake functions. The decomposed impedance is then transformed back into time domain and, thus, converted into an effective wake function which is by nature physical and most consistent with the numerical wake potential. Though the method is limited by the initial numerical impedance data and the choice of impedance decomposition, the retrieved wake function can be used in instability simulations with a bunch whose length is comparable to that used in the electromagnetic field solver. We show that the method can be applied to a general 3D structure, which allows finding effective wake functions of realistic vacuum chambers.

Funding:∗ Capital funding from CFI (Canada Foundation for Innovation). ** Funded under a contribution agreement with NRC (National Research Council Canada).The new radioisotope facility at TRIUMF, ARIEL, under construction, comprises two primary driver beams: 50 MeV electrons from the SC linac and 480 MeV protons from the main TRIUMF cyclotron. New 80 m long proton beam line will transport up to 100 microamps beam from existing cyclotron extraction port to an ISOL target station. H− cyclotron stripping foil extraction allows to feed this additional user simultaneously with 3 present different experimental programs. Distinctive features of the new beam line include: a) compensation of the cyclotron energy dispersion; b) low-loss (< 1 nA/m) beam transport after a collimator dedicated to remove the beam halo produced by large-angle scattering in the extraction foil; c) broad range of beam size variability at the production target by applying beam rastering at 400 Hz; d) sharing the same tunnel with electron beam line that requires unique beam loss protect system. Details of beam optics design as well as beam instrumentation are discussed in the paper.

Funding:Supported partly by the National Natural Science Foundation of China (Grant No. 11375273 and 11475269) and by the Ministry of Science and Technology under Grant 2016YFC0105300.There are very strong demand for mid-energy of proton machine recent years due to the surging cancer patients and fast progress of the space science in China. For the applications of proton therapy and proton irradiation, the energy range of proton beam usually is from 200 MeV to 250 MeV, or even higher for astronavigation. Based on the R&D starting from 2009, two construction projects of 230 MeV and 250 MeV superconducting cyclotron, which have been implemented recently at China Institute of Atomic Energy(CIAE). That was started in Jan 2015 for the 230 MeV machine, for the program of proton therapy and space science launched by China National Nuclear Corporation (CNNC), and in Jan 2016 for the 250 MeV machine, for the program of proton therapy launched by the Ministry of Science and Technology of China (MOST). In this paper, the designs for the two SC cyclotrons and their key components, including the main magnet, SC coils, RF system, internal ion source and central region, extraction system, etc, and the construction progress of the machines will be presented.

To enhance the performance and precision of TRIUMF Low Level RF system, a frequency/phase detector and counter based on FPGA is developed. The frequency/phase detector and counter is designed as a daughter board of the low level RF control system, and is connected to the mother board with mixed signal connectors. It sends the frequency error data to the PC though VXI databus, and provides two analog phase errors outputs. In current design, one single unit supports four channel discriminations of RF frequencies/phases. Preliminary tests show that the reported phase detector has a bandwidth of 400MHz. A unique implementation of frequency discrimination was carefully carried out to ensure the resolution can reach as high as 1Hz. The phase-frequency detector has been successfully applied to the Accelerator Cryo Module (ACM) system and the requirement of the low level RF control system is satisfied. After a long-term running test, the stability and reliability of the phase-frequency detector are verified.

Space-Charge Hamiltonian with a Space Coordinate as Independent Variable

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T. Planche, P. M. Jungpresenter, S.D. Rädel
TRIUMF, Vancouver, Canada

We present a version of the Low Lagrangian tailored to treat space-charge effects in particle accelerators: the Lagrangian is relativistic and uses a space coordinate as the independent variable. From this Lagrangian we obtain the corresponding Hamiltonian. From the Hamiltonian we obtain equations of motion for the 8 canonical variables, which can be plugged into a symplectic numerical integrator. We will finally discuss the possibility of numerically solving this problem using an explicit symplectic integrator.

The two-dimensional coefficients (resonance basis) in the Fourier expansion of the long-range beam-beam Hamiltonian have been expressed through the (less familiar) generalized modified Bessel functions of two arguments. We describe an efficient method to compute these coefficients based on the above representation. The method has been applied to HL-LHC lattices and benchmarked against MadX simulations of detuning.

Funding:TRIUMF receives federal funding via a contribution agreement through the National Research Council of CanadaThe TRIUMF 500 MeV cyclotron delivered routinely a total current up to 200 μA protons for 15 years till 2001. Since 2002, developments towards 300 μA total extraction became compelling because of the ISAC expansion. To meet future requirements (for addition of a new beam-line), a total extraction of 310 − 450 μA shall be envisioned. With such an increase of beam current, the space charge effect becomes a major concern in the centre region, as it limits the maximum amount of beam current achievable out of the machine. Therefore, numerical simulation on beam orbits with the space charge force has has been initiated, starting from the injection gap. This study is focused on the beam bunches which are very long compared with transverse size (because TRIUMF extraction is by stripping of H-minus and separated turns are not required). In order to achieve an improved understanding of the space charge effect, we worked to validate the simulations performed without and with the space charge force, using realistic centre region geometry. Our goal is to work out the space charge limits and their dependence upon the bunchers, rf voltage, and matching. In this paper we present our recent progress in this study.

Funding:TRIUMF receives federal funding via a contribution agreement through the National Research Council of CanadaThe second order linear coupling resonance nur-nuz=1 is driven by an asymmetry in the median plane of the cyclotron due to presence of the first harmonic in Br component. In TRIUMF cyclotron, this resonance is encountered at about 166 MeV and 291 MeV, where nur=1.2 and nuz=0.2. When the beam is off-centered radially to pass through this resonance, the radial oscillation gets converted into vertical oscillation, which can cause beam loss to occur, though these loss modes do not reduce the machine transmission under normal operation. In this paper, we present the results of simulations and measurements that we have performed to correct this resonance by using the existing harmonic coils.

Envelope Calculations on the Ion Beam Injection and Extraction of CANREB EBIS

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M.H. Pereira-Wilson
UW/Physics, Waterloo, Ontario, Canada

R.A. Baartman, S. Saminathanpresenter
TRIUMF, Vancouver, Canada

An electron beam ion source (EBIS) is being developed as a charge state breeder for the production of highly charged ions in the CANREB (CANadian Rare isotope facility with Electron Beam ion source) project at TRIUMF. The multiple tunable electrodes of the EBIS, coupled with the necessity of directing both an electron beam and an ion beam of varying charge, impose a challenging task for the optimization of the beam optics. With this in mind, beam envelope simulations have been performed to determine the acceptance of the EBIS and the emittance of the extracted ion beam. The electric field of the different EBIS electrodes were modelled using finite element analysis software and the envelope simulations were executed using beam envelope code TRANSOPTR. Preliminary results show envelope calculation as a viable candidate for tuning the injection and extraction optics of the EBIS.

Diurnal-like transmission variations in the ISAC-I warm accelerator system necessitates periodic retuning by operators. While beam loss points are well known, re-tuning nevertheless results in additional downtime and reduced count rates at experiments. This has motivated the development of an end-to-end simulation of the ISAC-I linear accelerator (linac) system to understand and characterize the nature of transmission instabilities spanning several hours to days.

Funding:Work supported by the BMBF under contract no. 05K13PEB.YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. The most recent revision of YACS now supports arbitrary order basis functions for the geometry and field discretization. In earlier revisions of YACS spurious modes were introduced by increasing the order of either the geometry or field basis functions. To prevent the emergence of spurious modes, YACS now matches the function spaces of the in-plane and out-plane function basis, and thus yields spurious free solutions. To demonstrate the capabilities of YACS, extensive cavity characterization studies on curved multicell microwave cavities are presented. Due to the combined utilization of the rotation symmetry, higher order basis functions and curved elements, eigenfrequency spectra above 10 GHz for L-band multicell structures can be easily obtained.

The slow orbit feedback at the electron storage ring at DELTA will be upgraded with new software. Finding a set of dipole-field-strength variations which minimize the deviation of the orbit from a reference orbit requires solving a convex optimization problem subject to inequality constraints. This work focuses on exploiting properties of a special type of interior point methods, which can solve this problem, for orbit correction at DELTA. After comparing runtimes of an interior point method to a Newton-like optimization algorithm, the performance of the new slow-orbit-feedback software is assessed based on measurement results.

Funding:Work supported by the BMBF under contract no. 05K13PEB.Since 2008, longitudinal coupled-bunch instabilities are suppressed at DELTA by a modulation of the phase of the accelerating RF field inside the cavity. To achieve a deeper understanding of the interaction of both effects, experimental studies have been made in 2016. These studies show a quadratic dependency of the coupled-bunch mode damping rates on the phase modulation amplitude. Recently, a numerical particle tracking code has been developed to confirm the experimental results. It is based on long range wake field effects produced inside an RF cavity acting on multi particle bunches of arbitrary charge, together with phase focusing by a phase modulated accelerating field. The numerical results confirm the quadratic dependency of damping rates on the phase shift obtained in experimental studies before.

Funding:This work was supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract Nos. DE-SC0013190, DE-AC02-05CH11231, and KC0407-ALSJNT-I0013.The thermal limit of the intrinsic emittance of photocathodes represents an important property to measure experimentally and to understand theoretically. Detailed measurements of intrinsic emittance have become possible in momentatron experiments. Moreover, recent developments in material design have allowed growing photoemissive layers with controlled surface roughness. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking. We aim to bridge this gap by developing realistic models for different materials in the three-dimensional VSim particle-in-cell code. We have recently implemented modeling of electron photo-excitation, transport, and emission from photoemissive layers grown on a substrate. We report results from simulations with these models on electron emission from antimony and gold. We consider effects due to density of states, photoemissive layer thickness, surface roughness and how they affect the spectral response of quantum yield and intrinsic emittance.

Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90° condition of phase advance is associated with a fourth order single particle resonance and the 120° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120° dispersion instability, which should be avoided during bunch compression.

Results are presented from end-to-end simulation of a 100 MeV strong focusing cyclotron (SFC). The develop-ment of the high-current SFC is motivated by applica-tions for production of medical isotopes and for a proton driver for subcritical fission. It uses a novel superconducting cavity to provide suffi-cient energy gain to fully separate all turns. An arc-contour F-D doublet, trim dipole winding, and sextupole are located along each turn within the aperture of each sector dipole to control the betatron and synchrotron motion and to stabilize non-linear dynamics with high-current operation. The phase space evolution of a proton bunch in the SFC was simulated using both the code OPAL and an ad hoc Runge-Kutta tracker. Iterative optimization of the dipole, quadrupole, and sextupole fields was used to provide precise isochronicity, favorable betatron phase advance, and cancellation of dispersion in each cell.

Funding:LIV. DAT is supported by the STFC under contract ST/P006752/1.The Liverpool Big Data Science (LIV. DAT) Center for Doctoral Training (CDT) is a hub for training students in managing, analysing and interpreting large, complex datasets and high rates of data flow. LIV. DAT offers a unique training approach addressing some of the biggest challenges in data intensive science to tackle a growing skills gap. It currently provides training to a cohort of almost 20 PhD students. Their research projects address R&D challenges in astronomy, nuclear, particle and accelerator physics. This contributions presents initial research results from modeling studies of the physics and biology of proton beam therapy using a Monte Carlo approach, as well as plasma-beam interaction in the cases of AWAKE and EuPRAXIA.

Funding:This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.The luminosity performance of the JLEIC design is achieved by using a high bunch repetition rate (476MHz) with moderate bunch charges, similar to the strategy employed in modern lepton colliders. Such a bunch configuration will make single bunch instabilities less probable, yet makes the machine more prone to the onset of longitudinal and transverse coupled bunch instabilities. Consequently, this will set higher demands on the bunch-by-bunch feedback systems to mitigate the multi-bunch instabilities. In this paper we present our detailed analysis of the growth rate of the coupled bunch instabilities for beams in both the electron and ion rings in JLEIC at the collision scenario. The implication of the growth rate on the feedback system will be discussed.

Funding:This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.JLEIC is the high luminosity and high polarization electron-ion collider (EIC) currently under active design at Jefferson Lab. It aims at high luminosity (1033~1034 cm-2s−1) for a wide range of ion species and center-of-mass energies. This luminosity performance relies sensibly on beam stability with high intensity electron and ion beam operation. The impedance budget analysis and the estimations of the single and multibunch instabilities are currently underway. In this paper, we present the update status of estimations for the longitudinal and transverse coherent instabilities, and identify areas or parameter regimes where special attentions for instability mitigations are required.

Funding:This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.We outline the recently redesigned booster for the pro-posed Jefferson Lab Electron Ion Collider (JLEIC). This booster will inject protons (or ions of equivalent rigidity) at 280 MeV and accelerate them to 8 GeV kinetic energy. To avoid transition crossing, the booster uses flexible momentum compaction (FMC) lattices to raise the transi-tion gamma above the reach of the machine. We also include several families of sextupoles to simultaneously control the chromaticities, and nonlinear dispersions that were excited by the FMC cells.

Funding:Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.The bunched beam electron cooler ring for the Jefferson Lab Electron-Ion Collider (JLEIC) requires a merger system to transport magnetized electron beams of two different energies to the same energy recovery linac (ERL) beamline. The system is especially challenging compared to existing mergers for ERL or hadron cooling applications (as at COSY) due to the small separation in energy between the two beams; for the JLEIC bunched beam cooler, the two beam energies may only differ by a factor of 4. An additional complication is the use of a magnetized beam. A toroidal merger system is studied using G4Beamline/GEANT4. Preservation of the quality of the low energy beam from the injector is especially vital for efficient cooling performance and compatibility with the ERL. Effects of the toroidal system on transverse and longitudinal emittances of the magnetized beams, as well as space charge effects, are presented and discussed.

Funding:Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.Historically, nearly all energy recovery linacs (ERLs) built and operated were used to drive a free-electron laser (FEL). The requirement for high peak current bunches necessitates bunch compression and handling the attendant beam dynamical challenges. In recent years, ERLs have turned from being drivers of light sources toward applications for nuclear physics experiments, Compton backscattering sources and strong electron cooling. Unlike an FEL, these latter uses require long, high charge bunches with small energy spread. The electron bunch must maintain a small projected energy spread and therefore must avoid gross distortion due to CSR and longitudinal space charge over a single (or multiple) recirculations. Accurately modeling the relevant collective effects in the system 'space charge, microbunching instability, CSR and the effect of shielding' in addition to beam dynamical processes such as halo, presents a formidable challenge. Absent a code that models all of these effects, we outline an approach towards the design, analysis and optimization of the high-energy electron cooler for the Jefferson Lab Electron-Ion Collider and survey widely used codes and their capabilities.

Two electron beamlets, also referred as two-bunch train with adjustable time and energy spacing are popular in many applications such as two color FEL and pump-probe experiments. We investigate compression of two-bunch train via velocity bunching scheme in a traveling wave accelerator (TWA) tube by varying the phase of TWA tube in a very large range. Beam dynamics simulations show that when the phase injected into the accelerator tube for the beam is set to ≪-100 degree, velocity bunching occurs in a deep over-compression mode, where two-bunch train is continuously tunable in time and in energy space, and the emittance of each sub-bunch is also preserved. In the experiment, we use energy spectrum and defecting cavity to diagnose the train's energy space and time space respectively, the measurements demonstrated that two-bunch train through deep over-compression scheme is separated both in time and in energy space, which also agree well with the predictions.

The magnets are being constructed for Xi'an Proton Application Facility (XiPAF) synchrotron. A study is started to obtain the specifications and tolerances of the magnets to avoid beam lost by the excessive magnetic field errors. The study includes the effect of field and alignment errors of the magnets on the closed orbit and beam optics. Also a preliminary study of effect due to multipole components in dipole and quadrupole magnets on dynamic aperture has been done. The tolerances of dipole and quadrupole magnets on field errors, including multipole components, and alignment errors are described in this paper.

In this paper we consider mathematical and computer modeling of nonlinear dynamics of particle beams in cyclic accelerators in terms of the matrix representation of the corresponding nonlinear differential equations. The proposed approach is different from the usual presentations of non-linear equations in the form of Taylor series. In the paper, we use the coefficients representation in the form of two-dimensional matrices. The similar approach allows us not only to significantly reduce the time spent on modeling beam dynamics but use symbolic mathematics to calculate the necessary two-dimensional matrices. This method demonstrates the effectiveness when solving problems of dynamics problems and optimization of control systems, and for evaluating the influence of various effects on the dynamics of the beam (including taking into account the spin). Using the tools of symbolic computations not only significantly increases the computational efficiency of the method, but also allows you to create databases of "ready-made" transformations (Lego-objects), which greatly simplify the process of modeling particle dynamics. Examples of solving practical problems are given.

Funding:HL-LHC project, European Circular Energy-Frontier Collider Study, H2020 programme (Grant 654305), Swiss State Secretariat for Education, Research and Innovation (SERI), Beam project (CONACYT, Mexico).Study of the head-on and long-range beam-beam effects in the High Luminosity LHC (HL-LHC) is of interest to evaluate their potential impact on performance (in the form of luminosity imbalance) and machine operation (collimator system), and, depending on their magnitude, correction schemes might be necessary to minimize them. In this work, both the β-beating at zero amplitude and its amplitude-dependence are computed for the current HL-LHC baseline optics and parameters, as well as the amplitude detuning, at the main interaction points and collimators. Correction of the β-beating, tune shift and footprint for the HL-LHC, as originally proposed for the LHC, via compensation of the multipolar terms of the beam-beam force with corrector magnets, is also discussed.

GIOTTO is a code based on a Genetic Algorithm, being used in the field of particles accelerators for some years*-***. Its main use concerns beam-dynamics optimizations for low energy linacs, or injectors, where the beam space-charge plays an important role on its dynamics. Typical optimizations regard the Velocity Bunching technique or, more generally, the emittance and energy spread minimization. Recent improvements in GIOTTO, here discussed, have added the important capability to solve problems with a wide research domain, making GIOTTO able to design a beam Transfer Line (TL) from scratch****. The code, taking as input the TL length and the optics elements, can define the correct lattice of the line that transports and matches the beam from the linac to the undulators of an FEL, finding the right gradients, positions and dimensions for the optics elements by exploring the parameters values in selected ranges. Further, the introduction of Twiss parameters into the fitness function makes GIOTTO a powerful tool in the design of highly different beam lines. Lastly, a new routine for the statistical analysis of parameters jitters effects on the beam is under development.*Bacci et al, NIM-B, 263, 488 (2007) **Bacci et al, presented at PAC'07, THPAN031 ***Bacci et al, presented at IPAC'16, WEPOY039 ****Rossetti Conti et al, NIM-A (2018, in press)

Funding:Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright BeamsIn order to maintain beam quality during transport through a storage ring, sextupole magnets are used to make chromatic corrections, but necessarily introduce deleterious effects such as nonlinear resonances and reduced dynamic aperture. Implementing intricate sextupole distributions to mitigate these effects will rely on precision beam-based measurement of the applied sextupole distribution. In this work, we generalize previous sextupole mapping techniques by using resonant phase-locked excitation of the beam at the Cornell Electron Storage Ring (CESR), which accounts for variations in the normal mode tunes on a turn by turn basis. The methods presented here are applied to simulation and actual turn by turn data in CESR for both simplified and realistic sextupole distributions.

Collective instabilities pose a major threat to the quality of the high brightness electron beams needed for the operation of a free electron laser. Multi-stage bunch compression schemes have been identified as a possible source of such an instability. The dispersive sections in these compressors translate energy inhomogeneities within the bunch into longitudinal charge density inhomogeneities. In conjunction with a collective force driving locally density-dependent energy modulations this leads to intricate longitudinal beam dynamics. As a consequence of the thin shape those bunches form in the longitudinal phase space, efficient simulation of such systems is not straight forward. At high resolutions, the numerical representation of the phase space density on a uniform grid is too wasteful, due to the large unpopulated phase space regions. In this contribution we present advances made in the development of a simulation code that addresses the problem of sparsely populated phase spaces by means of quadtree domain decomposition. A focus lies on the explanation of the underlying tree data structure.

The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment aμ with an unprecedented precision of 140 parts per billion (ppb), a four-fold improvement over the 540~ppb precision obtained by the BNL Muon g-2 Experiment. This study presents preliminary work on estimating the muon losses by using double coincidences in the calorimeters.

The impacts of coherent synchrotron radiation (CSR) and space charge in the bunch compressor section of the CLARA Free Electron Laser (FEL) are expected to be significant, given the relatively high charge and short bunch lengths expected. The General Particle Tracer (GPT) code allows for the modelling of these effects in tandem, presenting an opportunity to more reliably estimate their effects on the CLARA beam. To provide confidence in future studies using GPT, a benchmarking study on the CLARA Phase 1 beamline is presented alongside relevant simulations. This study will make use of pyroelectric detectors to measure the emitted coherent power of the CLARA beam as it passes through a dispersive section whilst varying the chirp imparted on the bunches longitudinal phase space (LPS). Simulations presented demonstrate the viability of such a study, with energies between ∼ 10-100 nJ per pulse expected to be incident upon the detector face.

Funding:Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program.An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring.

Funding:Travel was supported by the NSF, the APS DPB, and TRIUMF. Funding for the work was provided through DOE-HEP Award DESC0010301, NSF Award PHY1414681 and the NSF GRFP program.Design of accelerator lattices with nonlinear integrable optics is a novel approach to suppress transverse resonances and may be crucial for enabling low-loss high-intensity beam transport. Lattices with large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, have reduced response to resonant driving perturbations [*]. This paper describes preparations for tests of a quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). The planned tests employ a low-current highemittance beam with low space charge tune shift (∼ 0.005) to probe the dynamics of a lattice with large external tune spread (∼ 0.26).* V. Danilov and S. Nagaitsev, Nonlinear accelerator lattices with one and two analytic invariants, PRSTAB, 13, 084002, 2010.

Funding:Work supported by DOE under DE-SC0018008We consider the numerical evolution of Bloch equations for the polarization density in high-energy electron storage rings. Equilibrium polarization is well characterized by the DK formulas for current rings, but deviations may be important at the high energies we have in mind. We believe the Bloch equations derived in* give a more accurate description at all energies. These form a system of three coupled linear partial differential equations for the three components of the polarization density. Following** we formulate the equations in action-angle variables and approximate the Fokker-Planck terms. We aim to integrate these equations numerically in order to approximate the equilibrium and compare with the DK formulas. The smoothness and simple geometry of the problem makes it amenable to pseudospectral discretization using Fourier modes in the angles and Chebyshev polynomials in the actions, leading to a large ODE system. We will explore time stepping algorithms for the needed long time integration. Here, we present results for simple models checking the accuracy of the numerical method but note that our ultimate goal is to simulate polarization in the FCC and CEPC rings.* Ya.S.Derbenev, A.M.Kondratenko, Sov. Phys. Dokl., 19, p.438 (1975). ** D.P.Barber, K.Heinemann, H.Mais, G.Ripken, A Fokker-Planck treatment of stochastic particle motion…, DESY-91-146, 1991.

The Future Circular Collider (FCC) design study aims to develop the designs of possible circular colliders in the post LHC era. In particular the FCC-hh will aim to produce proton-proton collisions at a center of mass energy of 100 TeV. Initial tracking studies for the FCC-hh lattice at collision energy including field errors on the final focus triplet showed a very low dynamic aperture, most likely affected by the large beta functions and integrated length of the quadrupoles. Using non-linear correctors, the dynamic aperture was increased to acceptable levels; however, the difficulty to have an accurate magnetic model of the magnets required for this correction motivates the development of alternative methods. This work explores the possibility to increase the dynamic aperture by optimizing the phase advance between the main interaction regions. The description of this method along with its impact on the dynamic aperture will be given on this paper.

We have proposed a multi-bend achromat (MBA) lattice concept, called the MBA with interleaved dispersion bumps, in which two pairs of interleaved dispersion bumps are created in each lattice cell. Due to that many nonlinear effects can be effectively cancelled out within one cell and also many knobs can be used for nonlinear optimization, this MBA concept has given both large dynamic aperture (DA) and large dynamic momentum aperture in the lattice design of the Hefei Advanced Light Source (HALS). In this paper, to further enlarge DA, we extend the concept to the case of a super-period lattice consisting of two cells. In the super-period lattice, there are 1.5 pairs of bumps in each cell. A super-period 7BA lattice is preliminarily designed for the HALS, and a larger DA is obtained.

In recent years, multi-bend achromat (MBA) lattices have been widely used for the design of diffraction-limited storage rings (DLSRs) being developed around the world as the next-generation storage ring synchrotron sources. To better solve the problem of very serious non-linear dynamics in the DLSR lattice design, recently we proposed a new MBA lattice concept called the MBA lattice with interleaved dispersion bumps *, which was then applied to designing 7BA lattices for the Hefei Ad-vanced Light Source (HALS), with the result showing rather good nonlinear dynamics performance. In this paper, a 9BA lattice also following our MBA concept is preliminarily designed as a possible option for the HALS with a natural emittance of less than 30 pm·rad. Since generally the 9BA lattice can have a much lower emit-tance than the usually used 7BA lattice, the work in the paper will provide an inspiration for the existing third-generation synchrotron sources to upgrade to DLSRs with much lower emittances.* Zhenghe Bai et al., MOPH13, Proc. SAP2017, Jishou, China, 2017.

An elliptically polarized undulator (EPU) was applied to obtain high-brightness coherent synchrotron radiation at the upgraded Hefei Light Source, HLS-II. However, the EPU has serious dynamic effects on the beam performances including close orbit, emittance and dynamic aperture etc. when installed at the storage ring. In order to understand the effects, a Taylor expanded generating method was adopted to generate a fast and symplectic map for particle tracking. As for the compensation of the EPU, striplines were equipped above and below the vacuum chamber to reduce the nonlinear effects. With the symplectic tracking routine and the surface fitting method, different parameters such as dynamic aperture and the driving terms, could be set as the objective function to accomplish the optimization of the EPU.

We proposed and tested a scheme to measure and correct linac optics by scanning the beam trajectory in the horizontal and vertical phase spaces. The trajectory data are compared to tracking data in a fitting scheme, from which we can derive the quadrupole strength errors. Simulation is carried out to evaluate the requirements and the performance of the method. The method is experimentally applied to FEL linacs.

Ultrafast Electron Microscopy (UEM) can provide snapshot images of a dynamic process in samples with an ultrafast time resolution, which is shorter than picosecond. The Future Accelerator R&D Team at KAERI has been preparing a UEM facility with a photo-emission S-band (= 2856 MHz) RF gun by collaborating with GIST and KRISS. To achieve a higher spatial resolution as well as a higher time resolution, the transverse beam emittance, beam divergence, and energy spread should be smaller, and the bunch length should be shorter. Beam dynamics simulations with ASTRA code is used to optimize those beam parameters in the RF gun. In this paper, we describe ASTRA optimizations of the S-band RF gun to achieve high spatial-temporal resolutions for the UEM facility.